Furnace



c. L. :Fsr-:N ET AL Nov` 3, 1931 FURNAGE Filed Deo. 18. 1928 2 Sheets-Sheet 2 Patented Nov. 3, 1931 UNITED STATES PATENT or-'Flcal CARL L. IPSEN AND JAMES L. MCFARLAND, OF SCHENEOTADY, NEW YORK, ASSIGNORS TO GENERAL ELEGTRIC COMPANY, A CORPORATION OF NEW YORK FURNACE Appiieatmn med December 1s, 192s. seran No. 326,833.

Our invention relates to furnaces, more particularly to furnaces of the conveyer type, such as used in various enamelling processes and has for its object the provision of a simple, reliable and efficient furnace in which a substantial part of the heat stored in the articles which have been baked may be conserved and utilized. l

.Vitreous enamelling operations require a very close temperature control and a very uniform heat distribution. Thus, an accurate thermal control and proper heat dis` tribution are required for the production of uniform Work, maximum output and satisfactory operating costs. Our invention in one of its aspects, therefore, contemplates the provision of a furnace so constructed that it will inherently permit a close and accurate temperature control and will provide a uniform heat distribution.

In addition to these requirements with respeet to the heat control and distributlon, 1t is necessary to so support the articles that very little of their surfaces to be treated will be unexposed to the source of heat. Another aspect of our invention, therefore, is` the prolvision of conveying means for supporting the articles so that very little of the surfaces of the articles to be enamelled will be loft unexposed. Moreover, we arrange the conveying means so that the articles belng 'fed through the furnace will be held i n a vertical position regardless of irregularlties. 1n .the conveyer track or regardless of 1ts molina- In carrying our invention into effect in one form thereof we provide an electrical heating chamber of substantially hair pin shape and' mount suitable heating units within the chamberA so as to substantially cover the walls the stored heat will be employed to preheat the cold incoming articles by direct heat transfer. Preferably, the heating chamber will be located at a higher elevation than the passages through which the articles are conveyed to and from the heating chamber so that a' heat pocket will be formed which will be practically undisturbed by air or gas currents.

Moreover, to further enhance the efficiency of operation in that a more uniform product 'vill be obtained, we provide suitable conveying means for the articles providing for point contact therewith so that for all practical purposes their entire surface will besubjected to the firing operation. The articles will be held in a vertical position as they are moved throughout the furnace so as to eliminate any possibility of the articles slipping from the point contact supports during the baking process.

For a more complete understanding of our invention, reference should be had to the accompanying drawings in which Fig. l is a plan of an electric conveying furnace embodying our invention; Fig. 2 is a vertical section of the furnace taken through the line 2 2 of Fig. 1; Fig. 3 is a plan in section of the furnace; and Fig. 4 is a vertical section taken through the. line 4 4 of Fig. 1.

Referring to the drawings, we have shown our invention in one form in connection with a conveyor furnace provided for firing a vitreous enamel coating on various articles, as

for instance, culinary equipment, the furnace being provided with a suitable heating chamber and a suitable regenerative chamber. As shown, the conveyer furnace is provided with a suitable heating chamber 10 (Fig. 2) and a suitable regenerative chamber 11.- A conveyer 12 is provided for carrying the articles, which are bein enamelled, into and through the regenerat1ve chamber 11, then through the heating chamber 10, whereby the articles which have been previously suitably covered by enamel will be thoroughly fired, and-thence out through the regenerative chamber to the exterior ofthe furnace.

As shown, the heating chamber 10 comrises a top wall 13, side walls 14 and 15, a

ottom wall 16 constituting the oven floor and a substantially semi-circular end wall 17. It will be understood that these top, side, bottom and end walls form a closed chamber having an opening at its end opposite the curved end wall 17 through which the articles to be baked may be conveyed into and from the heating chamber. It will also be understood that these walls forming the heating chamber will be heat insulated. Thus, the inner linings of these walls will be constructed of some suitable high refractory and mechanically strong heat insulating material such as clay fire brick. The outer layer of these walls will be constructed of insulating brick formed from a suitable insulating material, as for instance diatomaceous material. As shown, the end wall 17 is provided. with an opening 18 through which access may be had to the heating chamber. This opening will normally be closed by a suitable heat insulated cover 19.

The regenerative chamber 11 comprises a top wall 20, a bottom wall 21 and side walls 22 and 23, allof these walls being constructedY in substantially the same manner as those embracing the heating chamber 10. Thus, these walls will be provided with an inner lining of a high refractory and mechanically strong heat insulating material, such as clay fire brick, and an outer lining of a suitable insulating brick, as for instance bricks formed from diatomaceous material.

As shown, this chamber is provided with o en ends, one of which will be placed in dlrect communication with the open end of the heating chamber 10 while the other will serve as an opening through which articles may be conveyed into and from the furnace.

It will be readily understood that the wallsl delining the chambers 10 and 11 may be common to both of these chambers or that these chambers ma be separately formed and suitably joined 1n any desired manner. Moreover, it will be understood that these chambers will be constructed of suitable height and width to accommodate the articles to be enamelled. The entire outer surfaces of the furnace will be covered by a suitable protective casing 24. Preferably, this casing will be constructed of some suitable sheet metal, as'for instance, steel. The entrance end of the chamber 11 will be provided with a suitable cover plate 24a which will be provided with apertures through which the articles may be conveyed into and from the furnace.

The regenerative chamber 11 serves as a .passage Way through which the articles will heating chamber will serve as a source of heat which will be utilized in preheating the cold incoming articles. Preferably, the regenerative chamber 11 will be inclined upwardly with respect to the horizontal and will be connected with the heating chamber 10 at its upper end. Thus, as will be readily apparent, a closed heat chamber or pocket will be formed in the upper portions of the oven, this pocket being practically free from disturbing air and gas currents. This feature is of particular importance in securing accurate temperature control and uniform distribution of heat, both of which factors are necessary in order to secure uniform enamelled surfaces. It will be understood that the chamber 11 may be inclined at an suitable angle, the angle being determined y the requirements of the particular installation.

In order to secure uniform and efficient heating of the articles as they are passedl through the heating chamber 10, we provide a plurality of heating units which will practically cover the walls and the floor of the heating chamber and thus will practically surround the articles passed through the chamber so as to subject them to direct heat radiation. To this end we provide a suitable vertical divisional wall 25 centrally located within theheating chamber 10.r The wall 25 thus serves to divide the chamber 10 into two portions interconnected at one end by a passageway defined by the end of the division wall and the curved end Wall 17. Thus, the heating chamber will have a substantially hair pin shape. Suitable heating units 26, preferably of the resistor type, are suitably mounted upon the inner walls of the chamber, that is, those walls defined by the partition 25, and suitable resistor heating units 27 are mounted upon the outer wall 17 of the heating chamber. It will be understood that these resistor units 27 will be shaped to conform with the curvature of this outer wall. A plurality of suitable resistor u-nits28 are mounted within the floor of the heating chamber and, as shown, will occupy a substantial area of this floor so that these units togetherwith the units 26 and 27, will constitute an intensive heating source within a comparatively small heating chamber. ever, that the hair pin shape of this chamber provides a relatively long heating passage as compared with the overall length of the chamber.,

It will be understood that these heating units may be separately interconnected with a suitable source of electrical supply or that they .may be electrically interconnected with each other and with the supply source in any suitable manner. As shown, the units are electrically connected so that the units 26 and 28 `upon each side of the wall 25 will be connected in series with each other. Suitable terminals 29 (Fig. 2) are provided whereby It will be observed,'how

" 55, 33 is provided with a plurality of tapered the units may be connected to their source of Supply- The articles to be enamelled Will be conveniently carried .through the furnace by means of a suitable conveyer which will serve not only to carry the articles through the furnace continuously, but will also serve to provide point contact support for the articles and hold them in a vertical position regardless of the inclination of the regenerative chamber 11 with respect to the heating chamber 10. The conveyer comprises la suitable track 30 of substantially halr pin shape, the track being arranged to conform with the hair pin shaped heating chamber and with the paths through which the articles are to be conveyed into and out of the furnace. Thus, as shown, the track comprises parallel portions 30a and 30-6 which Will extend the full length of the regenerative chamber 11 and will be spaced so as to properly position the incoming train of articles with respect to the outgoing train of articles. Moreover, the track is positioned with respect to the heating units 26,' 27, and 28 so that the articles which will be conveyed through the heating chamber will be properly positioned with respect to these heating units. provided to engage the track 30, these hangers being suitably spaced along the track and inter-connected by some suitable means, as for instance the chain 32. This construction provides a very sturdy and inexpensive conveying construction and, of course, permits of a ready accommodation to the curvature of the track 30. It will be understood that, preferably, the track portions 30a and 30-12 will be joined exterior of the furnace so as to form a continuous closed conveyer track.

In order to support the articles so that practically their entire surface will be exposed to the source of heat, suitable carriers 33, shown as horizontal plate like members, are pivotally suspended from the hangers 31 by means of rods 34 which, as shown are pivoted at 34-a on the hangers 21. By virtue of this'construction, each carrier 33 will maintain its horizontal position regardlless of the inclination of the chambers 10 and 11. Moreover, these carriers .will maintain their horizontal positions regardless of the slight irregularities of track construction that 'are likely to occur. Each carrier pin like supporting members 35 upon which the articles 36 to be treated will be supported. Thus, these tapered pins 35 will provide point contact supporting members for the articles so that practically their en- -tire surface will be exposed. It will be observed that this supporting means for the articles 36 provides for a complete enamelled surface, it being impossible for the articles Suitable hangers 31 are the track 30, Will be passed through this continuous aperture with unrestricted movement. These apertures like the inner linings of the furnace Will be lined with suitable high refractory heat insulating fire brick'. In order to prevent the escape of heat from th`e interior of the furnace, suitable cover members 37 Will be provided to cover thisl continuous aperture.

It Will be understood that the Whole of the furnace will be provided with suitable.

supporting means, for as example, suitable structural supporting frame work. As shown, this frame Work comprises a plurality of columns 38 mounted upon opposite sides of the furnace, suitable beams 39 horizontally positioned in spaced relation beneath the heating chamber, and suitable beams/10 horizontally positioned in spaced relation above the furnace. The beams 39 positioned beneath the heating chamber 10 will be supported by a plurality of longitudinally extending beams 41. The inclined chamber 11 Will* be supported laterally by means of suitable supporting members 42 tied in position by the rods 43. This structural steel frame Work may be of any preferred and desired arrangement and it is believed unnecessary. therefore, for a proper understanding of this invention' to describe in detail the disposition of the columns and beams.

In operation, it will be understood that the enamel will be suitably applied to the surfaces of the articles to be treated. After the enamel has been applied, the articles will be conveyed through the furnace whereby the enamelwill be fired. The articles Will be mounted upon the carrier members 33 and conveyed through the regenerative chamber 11. Thus, as shown, the articles Will be conveyed in a continuous stream through the regenerative chamber toward the heating chamber b means of the track portion 30-a.. It Wil be observed that these incoming articles will be preheated by the l the regenerative chamber will be, say ap-v `proximately 25 C., its temperature at the incoming end of the heatingf chamber 10 will be approximately 67 5 C., 4its temperature in the curved portion or bend of the heating chamber will be approximately 795 C., its temperature in the exit end of the heating chamber will be approximately 865 C., While its temperature in the exit end of the regenerative chamber will be approximately 130 C. It will be observed that a steady tran `fer of heat will be maintained between the articles leaving the heating chamber at approximately 865 C. and those being conveyed into the oven at approximately 25 C. so that the temperature of the incoming articles will be approximately 675 C. in the initial portion of the heatin chamber. Thus, the incoming articles wil be heated from approximately 25 C. to approximately 675 C. by direct heat transfer from the highly heated outgoing articles. It will be understood. however, that these temperatures merely serve for purposes of illustration. Any desired temperatures within a wide range may be secured by proper proportioning of the oven chambers and heating units.

While we have described our invention as embodied in concrete form and operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that we do not limit our invention thereto, since various modifications thereof Will' suggest themselves to those skilled in the: art without departing from the spirit of our invention, the scope of which is set forth in the annexed claims.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric enamelling furnace comprising a heating chamber of substantially hairpin shape, means for conveying articles into one leg of said chamber and for conveying articles from the other leg of said chamber and a plurality of resistor units within said heating chambersubstantially covering the inner and outer side walls of said chamber and a substantial area of the iioor of said chamber -so that substantially the entire surfaces of the articles being enamelled are subjected to direct heat radiations.

2.y An electric enamelling furnace comprising a heating chamber, a vertical dividing wall within said heating chamber ex-y tending lengthwise thereof so as to give the chamber a substantially hairpin shape, means for conveying articles into said chamber on one side of said dividing wall and from said chamber on the other side of said dividing wall, heating units mounted upon and substantially covering the opposite sides of said dividing wall, heating units mounted upon and substantially covering the walls of said chamber opposite the respective sides of vsaid dividing wall and 'heating units Icoverfprising a heating chamber within one end thereof, said heating chamber Abeing of substantially hairpin shape, heating units within said heating chamber substantially covering the side Walls of said chamber and a substantial area of the floor of said chamber so as to subjecty substantially the entire surfaces of the articles being enamelled to direct heat radiations and means for conveying articles through said furnace and heatin chamber whereby said articles are conveye into and from said furnace in substantially parallel adjacent paths thereby providing far a direct transfer of heat from the articles being conveyed from said heating-chamber t'o the articles being conveyed to said heating chamber.

4. A furnace comprising an inclined re- .Y generative chamber,` a heating chamber l0- cated at the upper end of said regenerative chamber so as to provide a heat pocket within said chamber, a vertical central dividing wall within said heating chamber extending lengthwise thereof so as to give said chamber a substantially hairpin shape, heating units substantially covering said dividing wall and the outer side walls 4of said heating chamber, heating units coverin a substantial area of the Hoor of said heatlng chamber and means for conveying articles -through said regenerative chamber and heating chamber whereby said articles are conveyed into and from said regenerative chamber` in substantially 4adjacent parallel paths so that heat is transferred directly from the article being conveyed from said heating chamber to the articles being conveyed into said heating chamber. v y

5. A furnace comprising an inclined regen,- erative chamber, a heating chamber located at the upper end of said regenerative chamber so as to provide a heat pocket within said chamber, a vertical central dividing wall y wit-hin l said heating .chamber extending lengthwise thereof so as to give said chamber a substantially hairpin shape, a plurality of heating units substantially covering the inner and outer side walls of said heating chamber ,L

and a plurality of heating units covering a substantial area of the floor of said heating chamber so as to subject substantially the entire surfaces of the articles being enamelled to direct heat radiations and means for conveying articles through said regenerative chamber and said heating chamber'whereby said articles are conveyed into andfrom said regenerative chamber in substantially parallel adjacent paths so that heat is conveyed directly from the articles being conveyed from the heating chamber to thosabeing conveyed into said heating chamber, said conveying means providing for point contact with said articles.

6. A furnace comprising two parallel-extending straight chambers having lateral communication with each other and constituting a recuperating portion, a single chamber of substantially U-shape, located a`t one end of the two chambers and communicating v wall in said chamber extending centrally lengthwise throughout a portion of said chamber and having one end spaced from said closed end so as to divide the upper end of said chamber into two relatively short sections communicating with each other at said closed end, heating means within said sections supported by said dividing wall and the outer walls of said sections, and continuous conveying means for conveying articles through said elongated chamber to said heating sections and thence through one of said heating sections and the communicating passage between the sections to the other of said heating sections through which they are carried to and thence through said elongated chamber. the articles being carried to and from said heating sections in said elongated chamber in substantially parallel adjacent paths whereby heat is transferred directly from the articles being conveyed from said heating sections to those being conveyed to said sections. y

8. An enamelling furnace comprising an inclined elongated heating chamber. the upper end of said chamber being closed so as to provide a heat pocket within said chamber,

a wall in said chamber extending' centrally lengthwise throughout a portion of said,

chamber and having one end spaced from said closed end so as to divide the upper end of said chamber into two relatively short sections communicating with each other at said closed end, continuous conveying means for carrying articles through said`elongated chamber to said sections. and thence through one of said sections and the communicatingpassagewav between the sections to the other of said sections through which they are carried to and thence through said elongated chamber` and a plurality of heating units within said sections substantially covering the opposite sides of said dividing wall and the walls of said sections facing said sides so that substantially the entire surfaces of the articles carried through said sections are subjected to direct heat radiations, -the conveying means forfsaid articles providing for point contact therewith so as to provide for unobstructed heat radiation from said heating units to said articles.

In witness whereof, we have hereunto set our hands this 17th day of December, 1928. CARL L. IPSEN.

JAMES L. MCFARLAND. 

